Magnesium alloy and magnesium corrosion protection method
The reasons of Magnesium and magnesium alloys are the most difficult plating metals :
1. Magnesium oxide is easily formed on the surface of magnesium alloy and magnesium , it is not easy to clean and seriously affects the adhesion of coating
2. due to the electrochemical activity of magnesium is too high, all acidic plating solutions will cause rapid corrosion of magnesium substrate , or the replacement reaction strongly with other metal ions , the coating binding will become loose after replacement
3. The secondary phase (such as rare earth phase and Y phase) has different electrochemical characteristics, which may lead to non-uniform deposition.
4. the standard coating potential is much higher than the magnesium alloy substrate, and any through-hole will increase the corrosion current, leading to serious electrochemical corrosion, while magnesium electrode potential is very negative, it is difficult to avoid hydrogen evolution caused by pinhole during plating.
5. the tightness of die-casting Mg alloys is not very high, there are impurities on the surface, which may be the source of coating pores.
Electroplating or electroless plating is a Magnesium and Mg alloys surface treatment method to obtain superior corrosion resistance and electrical, electromagnetic and decorativeproperties at the same time.